Use webpack to deliver newest ACE editor

With this commit, we change the delivery method for the ACE editor from manually copied files to using yarn and webpack. As a side-change, we also modify how the mode is selected through JavaScript instead of Ruby.

Through webpack, the `modePath`, `themePath`, and `workerPath` are automatically determined and working as expected.

Closes #250

app/assets/javascripts/request_for_comments.js

@@ -57,11 +57,6 @@ $(document).on('turbolinks:load', function () {
         $(this).parent().toggleClass('collapsed');
     });
 
-// set file paths for ace
-    _.each(['modePath', 'themePath', 'workerPath'], function (attribute) {
-        ace.config.set(attribute, CodeOceanEditor.ACE_FILES_PATH);
-    });
-
     const commentitor = $('.editor');
 
     commentitor.each(function (index, editor) {